A positive displacement rotary machine (PDRM) (RU 2004133654) having a body with an internal ring cavity is known. A spiral separator with a rotor inside is installed in this cavity. The rotor working surface is a surface of rotation, where there is at least one slot along the rotation axis of the rotor, in each of which a piston partly extending (projecting) from one side of the rotor is rotatably mounted. Besides, the piston has at least one through-cutout across its perimeter interacting with the separator for the piston and the rotor rotation synchronization. The machine inlet and outlet openings are spaced along the rotor axis and separated from each other by the separator. The piston of such a machine rotates in the same direction relative to the rotor and together with the rotor rotates relative to the body.
Such machine has the following advantages.
The piston is securely installed in the rotor slot extending from it for about a halfway. The inlet and outlet openings spacing configuration along the rotor axis facilitates combination of such machines into multistage machines including those with a common rotor for multiple stages. Such machines are used in submersible units. The common rotor enables the reduction of radial load and often thrust load on the bearings of the rotor by balancing the loads on the individual stages in case the stages are turned relative to each other.
An essential advantage of the pump, produced on the basis of this machine, is the uniform flow rate.
Disadvantage of such machines is a complicated configuration of the separator and the piston through-cutout that does not allow contact between them over a large area in order to reduce wear of the friction pair (to reduce an ideal load on the friction pair and extend its service life).
A PDRM is known (GB 1458459 and similar to it DE 3206286 A1), the body of which contains a cavity in the form of a spherical segment, in which a separator shaped as a sector of a circle is installed along the axis of symmetry of the cavity dividing the cavity; a rotor installed inside the body and capable of rotation has the working surface in the form of two truncated cones resting with their tops on a sphere from the opposite sides, while on the surface of the sphere, at an angle to the axis of symmetry of the rotor, there is a circular groove positioned tangentially with respect to both cones. A piston with a through-cutout, allowing the passing through of the separator, is rotatably mounted in this groove. The piston interacts with the separator through a sealing synchronizing element (SSE), embodied in the form of a cylinder sectioned in half by a through-cutout, which begins at one end and extends most of the way to the other end. The working medium inlet opening and corresponding outlet opening are located on the same side of the piston. On the other side of the piston there is one more pair of inlet and outlet openings. The piston of such machine swings relative to the body and the machine rotor rotates relative to the swinging piston.
Such a machine has the following advantages: a good contact of the piston with the body chamber along the spherical surface, a good contact between the piston, the sealing element and the separator, simple geometrical forms: the flat separator, the flat piston and others.
PDRM also has disadvantages: the difficulty of combining such a machine into a multistage machine, associated with the fact that the inlet and outlet openings are located on the same side of the piston, and in order to get from one stage to another, a channel is required bypassing the spherical cavity of the body along the rotor axis. Also considered as disadvantages are: non-uniform flow rate, weak mounting of the piston (which is only partially located inside the groove on the sphere), which also weakens the shaft due to the circular groove, unreliable mounting of the sealing synchronizing element in the through-cutout of the piston (jamming is possible under increased loads).
The PDRM (DE 3146782 A1), having a body with a cavity in the form of a segment of a sphere and a rotatably mounted rotor with through-slot along the rotor axis, is known. There is also a piston in the form of a disk rotatably mounted in the rotor slot, a chamber in the form of spherical segment partitioned by a separator in the direction of the rotor rotation as well as outlet and inlet openings located in front of and behind the separator accordingly. Besides, the piston rotation is synchronized with the rotor rotation by means of a shaft, fixedly going through the rotor, and the system of gears, one of which is fixed at the piston. The piston of such a machine rotates in the same direction relative to the rotor and, together with the rotor, rotates relative to the body.
Advantages of this machine include spherical contact between the piston and the chamber, reliable mounting of the piston extending towards both sides from the shaft, presence of a strong shaft (longitudinal slot barely weakens it), possibility to arrange (to space) the inlet and outlet openings along the shaft to combine several stages on one shaft, independence of leakage (slippage) on the wear of synchronizing mechanism, and possibility of high rotational speed.
Unreliable synchronizing mechanism, especially in case if the gear shaft is required to pass through several stages, is referred to as disadvantage.
A new kind of pumps (drives, compressors), which is expected to be used in many fields (from oil and gas production, transport up to domestic needs), is declared by this application; below different embodiments of the machine components of the same function, meeting different requirements for manufacturing costs, reliability, service life and tightness are given. As the PDRM is designed to operate using different working liquids (from high-viscosity liquid with abrasive to gas), with different flow rates (size), at different speed, different methods of its operation (methods of the piston through-cutout closing off at the propulsion area) are claimed. A variety of embodiments is also associated with different capabilities of potential manufacturers.
Further is the description of the PDRM type, which appeared due to using a new operation method of the spherical PDRM (field of method applicability).
The purpose of this application is to describe the operation method of the spherical PDRM (having a body with a cavity in the form of a spherical segment, a part of which represents a working chamber surface), which allows making the flow rate of such a machine almost uniform (non pulsating) throughout the cycle and spacing working medium inlet and outlet openings along the axis of the machine rotor rotation (the latter allows convenient combining the separate stages of the PDRM into a multistage unit with the common rotor for an application in downhole submersible plants). The characteristic feature of this PDRM is the presence of at least one piston mounted in the rotor slot and performing rotational oscillations relative to the rotor and, together with the rotor, rotating in the same direction relative to the body. Structurally, such movement of the piston is provided for by the fact that a separator, partitioning a circular working chamber formed between the body and the rotor, is fixed inclined to the plane of the rotor rotation, and the rotor slot for the piston has the larger angle of inclination to the plane of the rotor rotation than the separator does. In most embodiments, the slot is located along the rotor axis. In the simplest case, the piston is a flat disk with a spherical side surface, the diameter of which is almost equal to the diameter of the body spherical cavity. However, (see below) the piston of differing thickness by radius and/or angle has to be used as well as a part of disk, for example, in the form of a truncated sector or disk with hollows in separate places can be used as the piston to improve some features. This is required, for example, to make possible of multiple piston installation, reduction of gaps by means of centrifugal forces, the piston weight-reduction due to removal of unused sections and so on. When using the piston in the form of a whole disk, the rotor slot for the piston is made to be through and the piston has two through-cutouts for the separator, located at approximate diametrically opposite ends of the piston. When using the piston in the form of a sector of a disk, the rotor slot for the piston can be made blind (it results in an increase of the machine flow rate), and the piston has one through-cutout for the separator. In the simplest case, the separator represents a flat washer, a working part diameter of which (it does not include the washer attachment to the body) is almost equal to the diameter of the body cavity and on the area of which through-passes (holes, slits) from one side (plane) of the washer to the opposite side are made. In extreme case, about a half of the washer is absent and one large pass is made in its place. This extreme case is logically to be referred to the same type of the machines and the area, left from the separator, is to be called the washer area, as the separator configuration is provided for by the piston through-cutout path, which still remains closed. Besides, the piston through-cutout traces out a closed path, running just around the rotor unlike, for example, principally spiral (about circular axis of torus) path of the piston through-cutout according to application RU 2004133654 and unlike the other applications, where the through-cutout swings relative to the body. However, in some cases (see below), deviations from the flatness of the separator are useful. The simplest deviations are associated with a change of the washer thickness along its radius. They are associated with its strength properties and the strength properties of the mating parts as well as with the working cavity space saving. In some cases, a change of thickness along the circle is used and, rarer, to optimize inclination angles relative to tile piston or the piston speed at different portions of the machine cycle the washer deviation from flatness is used. The piston can be equipped with the seal synchronizing element (SSE), a part of which projects into one or both through-cutouts of the piston. It is referred to as the synchronizing element since it transmits a force from the separator to the piston to provide synchronization of the latter, and as the seal element since, having a higher possibility of tracing the inclination angle of the separator due to additional degrees of freedom, it provides a closer contact with the separator along the larger area. The SSE is logically to be considered as a part of the piston. Finally, one more deviation is the body cavity deviation from a spherical form, which is associated both with tolerances for manufacturing, allowances for possible system clearances (for example, for the shaft axial clearance) and with deviations from spheroid resulting in an increase of some characteristics because of the others. Thus, at several pistons in the form of the sector of a disk, the machine flow rate can be increased due to modifying the sphere into a barrel and, further, even into a cylinder. Besides, other features are smoothly changed: at first, the piston contact with the body wall gets worse and then becomes better on drawing near to the cylinder, the piston inertial load increases.
The main factors influencing the form and dimensions of the PDRM parts.
The rotor of this PDRM shall be solid (made as one rigid unit) for its adaptability to manufacture and in order to get maximum pressure (especially, in the multistage embodiment, when, via the rotor of the first or the last stages, maximum torque is transmitted from drive to all the rest stages). When possible, a slot for the piston is arranged, mainly along the axis of the rotor rotation, and made flat. The slight deviations in the slot angle and flatness are possible to provide the piston support area distribution for optimization of friction forces moment acting on the piston. The piston can be self-adjustable in such slot. That is, the rotor is mounted in the PDRM body due to its bearings and/or, for example, due to the spherical or other surfaces. Irrespective of the rotor, the piston is mounted in the PDRM machine (by the coordinate along the rotor axis and by the coordinate along the piston radius perpendicular to the rotor axis) supported by the body spherical surface and by the coordinate along the piston geometrical axis it is supported by the rotor slot. At such a mounting, requirements for the accuracy of the piston positioning in the rotor significantly decrease as well as the gaps, required for the machine operation, also decrease.
Besides, the piston is not desirable to be made too thick. As the piston thickness increase results in the rotor strength decrease as well as the piston torque increase over the required value, at the same time, reducing the machine flow rate (if additional actions, making the machine design more sophisticated and limited, are not taken).
The separator thickness decrease at the propulsion area of the body results in the machine output increase. At this area, the separator is, mainly under a light longitudinal load, while at the bypass area (where it separates the working medium inlet opening from outlet opening) it is under a large transverse load. The separator thickness at the bypass area of the body does not influence the machine output.
Only the ascending area of the separator, located at the bypass area, is used for its title-specified purpose (to separate the chambers of different pressure). Its descending area, located at the propulsion area of the body, to the contrary, shall pass the whole working medium flow through.
At the piston through-cutout sealing by means of the seal synchronization element (SSE), the geometrical axis of which goes through the piston center (the sphere center), the part of this element, projecting into the working chamber, shall be cut in two by the through-cutout to enable the separator to pass through; therefore, a sufficient area for secure fixing of these parts to a common base shall be provided for. The SSE shaft shall also be strong enough to withstand inadvertent overloading, caused by potential mechanical impurities ingress into the machine or temporary change of working medium properties.
Since the separator thickness increase (especially, in its central part) has a negative effect on the SSE strength, its thickness is desirable to be reduced. But the maximum pressure of the machine is determined by the strength of the separator (especially, of its ascending area). Therefore, a task of optimal partitioning of the separator into parts as well as maximum strengthened (rigid) connection of these parts arise. Besides, the separator flatness is desirable for adaptability to manufacture and manufacturing accuracy.
There are contradictory requirements in the fact that the SSE shaft shall be located inside the piston (not going beyond its thickness) and the base for fixing two projecting parts of the SSE is also desirable to be located inside the piston.
In the first PDRM embodiment, the piston through-cutout at the propulsion area is closed off by the descending area of the separator, on which the passes for working medium flow to the other side of this descending area are made. Moreover, angular dimension of the passes along the movement of the piston is limited (otherwise, the separator does not close off the piston through-cutout) resulting in working medium flow resistance increase. Later, another way of providing the piston through-cutout tightness at the propulsion area was found. The multiple means for the piston through-cutout closing off due to introduction of additional elements turned out to exist. In this application, only some of them are considered to illustrate the new method. Due to using the new method, angular length of the passes for working medium flow was significantly increased. In the limiting case, one large pass is made throughout the descending (propulsion) area of the separator.
The assigned task is achieved due to the fact that at least one portion of the piston through-cutout at the propulsion area is closed off by means of the additional elements, hereafter referred to as shutters, besides, the separator does not take part in the piston through-cutout closing off at this area. This results in increase of the working medium pass size, reducing the machine hydraulic resistance. And in many cases, this produces wear margin for the through-cutout and the separator, excluding the occurrence of the gap leakage.
The method is based on the fact that the height of the through-cutout is much smaller than the height of the machine chamber. Therefore, the shutter can be small as well as can perform slight rotational oscillations relative to the piston.
At small pressure differentials, the separator can be thin enough and thus, the piston through-cutout can also be thin. For the high-speed machine, there can be no need in the through-cutout mechanical closing off. Its hydraulic resistance is sufficient for this purpose. The optimal through-cutout entry and exit form is well known from the reference books.
The simplest means for the piston through-cutout closing off is sealing it by means of the flexible resilient member. Such a sealing is well suitable at small thickness of the separator (at small pressure differentials on the machine stage). The presence of the SSE in the through-cutout improves the conditions for performing such a sealing. Then, the sealing is mounted in the SSE through-cutout.
The following method is suitable for a high pressure as well. This is the mechanical shutter which rotates around the piston axis or close to it. There are several methods to control such a shutter.
1) The shutter has a tendency to be in a closed position due to centrifugal forces and/or the resilient members as well as due to forces coming from the liquid pressure differential on the piston. Besides, it has an elongated chamfered lug, by which it interacts with the projecting sharp end of the separator, resulting in its opening in due moment of time. Impact force can be reduced to a minimum (to zero) by the form of the lug and a chamfer. Flexible materials can be used for these parts. The shutter is desirable to be pressure unloaded before impacting. For this purpose, a recess, passing through which the piston loses tightness, is made in the body. Unreliability of closing and impacts resulting from the presence of the clearances in the system are referred to as disadvantages.2) The shutter lug moves all the time inside a guide groove, made on the body spherical surface, and entirely regulates the shutter position. The disadvantage is that the groove presence results in increase of the machine diameter (it is important for submersible embodiments) and leads to abrasive accumulation in it and rubbing of the lug. The lug rubbing results in seal deterioration.3) The position of the shutter is controlled by a guide, situated along the body at the propulsion area. The disadvantage is that the piston through-cutout shall also pass this guide through; therefore, it is bigger in size which results in increase of the shutter size and its load. A wear of the shutter cutout and the guide results in the seal deterioration.4) The shutter is controlled by the angle of the separator, located from the opposite side of the piston. For example, when the SSE, the axis of which goes through the piston center at right angle to the piston axis, acts as the shutter. The disadvantage is that along a sufficiently large transition area the angle of the separator is changed slowly delaying the closing off process.5) The shutter is controlled by the thickness of the separator, located from the opposite side of the piston. The disadvantage is that it results in an increase of the separator thickness, the piston through-cutout height and the shutter dimensions.6) The most interesting case is, when the shutter is controlled by the piston position relative to the rotor. The shutter is required to be brought into open position just at one point—at the place of the maximum deviation of the piston through-cutout, for example, downwards (if the shutter is located higher than the through-cutout is). In all the other positions, it is closed provided that it is not positioned at the separator. The advantage is that the piston speed relative to the rotor is not high (it is equal to zero at the center) and this place is protected against abrasive to a greater extent (by means of centrifugal forces, seals). The simplest way of controlling is to make a groove in the form of an arc near the axis of the shutter and to mount a pin (stop) in the rotor. When the shutter, together with the piston, comes to the position of the separator entry, the pin reaches the end of the groove and the shutter stops, but the piston can turn further.
The assigned task is achieved by making the SSE base conical.
The assigned task is achieved by making the chamfers (rounding) between the SSE through-cutout bottom and its side surfaces.
The assigned task is achieved by making the SSE through-cutout profile and, therefore, the separator profile thinner towards the machine center.
The assigned task is achieved by making the chamfers at the place where the rotor slot for the piston opens on the central sphere. As a result, stronger base of the SSE can be located in the space emerged.
The assigned task is achieved due to decrease (making the recess along a fin) at the joint of the rotor slot for the piston and the central sphere. As a result, stronger base of the SSE can be located in the space emerged.
The assigned task is achieved due to mounting the special washer, acting as sealing between the SSE, the piston and the rotor, into the piston through-cutout.
The assigned task is achieved by making the SSE part, projecting into the working chamber, in the form of a body of rotation (for example, cylinder plus cone or sphere), diameter of which is greater than the diameter of the SSE shaft.
The assigned task is achieved due to composing the piston of at least two parts (division can go along its end surfaces) at least on one of which a boss (increased thickness) is made, and there is a cavity for this boss in the rotor slot. It is different from the standard piston thickness increase in that it is hidden inside the rotor and its movement together with the piston along the rotor slot during the piston self-positioning does not result in increase of the gaps between the rotor and the piston.
The assigned task is achieved due to the separator partitioning into unequal parts (which is somewhat different from the conventional division into the ascending and descending areas). Besides, the ascending part is larger than the descending one. Moreover, the through passes can also be partly located at the ends of the ascending part.
The assigned task is achieved by making the SSE solid with its shaft, intersecting the chamber center. Moreover, the piston is made prefabricated, consisting of at least two parts (partitioning can go along its end surfaces).
The assigned task is achieved due to the fact that the lug is made in the region of the through-cutout bottom on the piston, and the rotor slot is enlarged in the center for allowing this piston lug passing through at assembly. The rotor slot enlargement area can be closed off by an additional member—an insert of the rotor, which is inserted in the rotor together with the piston. Additionally, in order to strengthen the piston, the boss can be made in its center. In this case, a recess or a through hole for the boss is additionally made in the rotor insert.
The elements similar in function are designated by the same numbers on all the figures, where:    1—body;    2—body part, ascending half;    3—body part, descending half;    4—spherical cavity;    5—concentric hole for rotor shaft outputs;    6—machine geometrical axis;    7—rotor;    8—piston;    9—separator;    10—ascending (bypass) part of separator;    11—descending (propulsion) part of separator;    12—inlet opening;    13—outlet opening;    14—duct without flow turning around body;    15—duct for flow turning around body;    16—spherical part of rotor above cone;    17—rotor surface in the form of a truncated cone;    18—central spherical part of rotor;    19—rotor shaft output;    20—working cavity;    21—rotor slot for piston;    22—body slot for separator;    23—rotor recess for SSE;    24—body spherical surface;    25—separator flat (conic) surface;    26—piston geometrical axis;    27—piston shaft;    28—piston flat part;    29—piston central thickened part;    30—piston through hole for SSE;    31—piston spherical side surface;    32—SSE geometrical axis;    33—piston through-cutout for separator;    34—piston end-face;    35—piston through-cutout bottom;    36—piston through-cutout side surface;    37—cylindrical surface on piston through-cutout side;    38—conical part of hole in piston through-cutout for SSE base;    39—piston cylindrical hole for SSE;    40—separator joint;    41—separator inner spherical surface;    42—separator through pass;    43—chamfer, connecting piston end-face with cylindrical surface on piston through-cutout side;    44—seal synchronization element (SSE);    45—SSE through-cutout for separator;    46—SSE lugs;    47—pin;    48—SSE flat or conical area;    49—SSE through-cutout side surface;    50—SSE through-cutout bottom;    51—SSE spherical end;    52—SSE conical base;    53—SSE shaft;    54—SSE shaft hole for pin;    55—chamber between SSE through-cutout bottom and SSE through-cutout side surface;    56—SSE inner spherical surface;    57—piston hollows for weight-reduction;    58—rotor slot flat surface;    59—rotor slot flat surface recess;    60—SSE cylindrical part.    61—chamfer at the joint of rotor central sphere and rotor slot;    62—piston hole of smaller diameter for SSE pin;    63—piston boss for its strengthening;    64—hole for rivet;    65—washer to be mounted into piston through-cutout;    66—washer flat (conical) side;    67—washer cylindrical bottom;    68—washer spherical top;    69—washer conical hole;    70—washer side mating with piston through-cutout;    71—groove at the joint of rotor central sphere and rotor slot;    72—chamfer at the joint of rotor central sphere and its conical part;    73—conical part of SSE body of rotation;    74—chamfer at separator inner part;    75—piston lug for SSE through-cutout closing off;    76—separator exit;    77—piston lug for SSE base;    79—resilient member in SSE through-cutout;    80—insert in the shaft;    81—separator entry;    82—rotor contact area;    83—separator entry for shutter;    84—separator exit for shutter;    85—piston cutout for shutter;    86—shutter;    87—rotor recess for shutter;    88—shutter lug;    89—shutter shaft;    90—shutter groove for stop pin;    91—resilient member for shutter drive.